Complex forming dewaxing composition and process



May 5, 1964 E. R. KERR ETAL COMPLEX FORMING DEWAXING COMPOSITION AND PROCESS Filed Sept. 25. 1960 .process isto be economical.

United states Patent o 3,132,084 COMPLEX F06 DEWAXING CGMlOSlTlN s AND PROCESS Edwin R. Kerr, Fishkill, and .lames K. Truitt, Beacon, NX., assignors to Texaco inc., New York, NX., a corporation of Delaware Filed Sept. 23, 1960, Ser. No. 58,141 12 Claims. (Cl. 208-25) y v- .This invention relates to a urea complex formation and/or` thiourea complex formation process and a complexing agent for usetherein. In accordance with one embodiment, this invention relates to a dewaxing process and a dewaxing agent for use therein. n Y

Itis known that urea is capable of forming solid corn- `plexes with straight chain hydrocarbons, particularly waxy straight chain hydrocarbons. lt is also known that thiourea is capable of forming solid complexes with nonstraight chain 'hydrocarbons such as the isoparains and alicyclic hydrocarbons. Various processes relying upon the complex formation properties of these compounds have been proposed for use in treating petroleum fractions, such as fuel oils, lubricating oils and the like. These processes have employed in association with the urea or thiourea a solvent which is also advantageously a solvent for the petroleum fractions being treated to act as an initiator for the complex formation reaction between the urea and/ or thiourea and the corresponding complexing hydrocarbons.

vlThe various methods suggested heretofore for dewaxi ing, relying upon complex formation of waxy hydrocarbons with urea and/or thiourea, have for the most part not been completely satisfactory. For example, the presence of an added solvent for the complex forming agent to act as an initiator or catalyst for the complex forming reaction leads to certain diliiculties since this solvent must be recovered from the reaction admixture if the Usually the solvent is recovered by fractional distillation, necessitating the use of relatively high temperatures at which the complex forming agent, urea and thiourea, tends to become'unstable and deteriorates.

Accordingly it is an object of this invention to provide an improved urea and/or thiourea complex forming process.

Another object of this invention is to provide a method for effecting the removal of straight chain hydrocarbons from petroleum fractions, such as kerosene, jet fuels, diesel oil, lubricating oil, etc. I

Another object of this invention Vis to provide a method for carrying out a dewaxing operation in the substantialV Yabsence of a solvent and relying upon a liquid treating agent which is capable of forming solid complexes with A waxy hydrocarbons during the dewaxing operation.

How these and other objects of` this invention are accomplished will become apparent in the light of the accapable of forming solid complexes with urea and/or thiourea.' Still in` accordance with this invention it has been discovered that a waxy petroleum fraction can be dewaxed by contact with a relatively low melting point admixture containing urea, thiourea and acetamide in the substantial absence of a solvent therefor or for one of the components of the admixture.

. is effected withinr complex breaker 21 by flowing a suit-I n arnesi 'Patented May 5., 1964 ICC In the practice of this invention admixtures containing respectively, by weight, from 20% to 45% urea, about 10% to 40% thiourea and about 25% to 60% acetamide are satisfactory as the complex forming agents.

In the practice of this invention admixtures having initial freezing points -in the range 76 to 120 F., and containing lby weight 29 to 35% of Aurea, 26% to 31% of thiourea and 45% to 34% of acetamide are particularly useful as complex forming or dewaxing agents for the treatment or dewaxing of mixtures containingl compounds which form complexes with urea or thiourea, such as petroleum fractions. Y

Y Referring now to the drawing whichschematically illustrates a dewaxing process in laccordance with a practice of this invention, a waxy charge oil is supplied via line 10 into contactor 11 where it is introduced into Contact with a molten admixture of urea, thiourea and acetamide having an initial freezing point below about F., the admixture of urea, thiourea and acetamide having been introduced into contactor 11 via line 12.

Within contactor 11 the waxy charge oil and molten admixture of urea, thiourea and acetamide are thoroughly admixed by means of agitator 14. While the waxy charge oil and the molten dewaxing agent admixture of urea, thiourea and acetamide are being commingled within contactor 11 the resulting reaction mixture is cooled by means of a suitable cooling fluid passed through heat exchange means 15 provided within contactor 11. As the temperature of the reaction admixture Within contactor 11 drops to the initial freezing point of dewaxing agent admixture of urea, thiourea and acetamide, the resulting formed solidified admixture containing solid urea and solid thiourea reacts with the waxy hydrocarbons present in the waxy charge oil to form the corresponding solid urea and/or thiourea-waxy hydrocarbon complexes.

After the reaction mixture has been cooled to a temperature below the melting point of the residual unreacted admixture of urea, thiourea and acetamide, preferably below about 76 F. and after the complex forming re-r action between urea and thiourea and the corresponding complex forming waxy'hydrocarbons in the charge oil has been substantially completed, the resulting cooled reaction mixture is transferred from contactor 11 via line 16 to filter 1S.

By means of lter 1S the resulting dewaxed oil is separately recovered and removed via line 19 and the remaining, filtered solids comprising solid urea and/ or thiourea waxy hydrocarbon complexes and solidified residual dewaxing agent containing urea, thiourea and acetamide are removed from filter 1S via line 20.

l Filter 18 may be any suitable means for effecting the separation of solids from a liquid. Advantageously, as'

schematically illustrated in the drawing, filter 18 is a rotary vacuum filter which can be continuously operated, the dewaxed oil being continually withdrawn or recovered via line 19 and the solids comprising complex and solidified residual dewaxing agent being removed from the filter 1S and transferred therefrom via line 20 to complex breaker 21.

Within complex breaker 21 the solids transported from lter 18 via line 20 are subjected to a suitable high temperature effective to break the solid complexes into their respective components urea and/or thiourea and the corresponding waxy hydrocarbons. The high temperature, such as a temperature above about 120 F., e.g. a temperature in the range to 150 F. or higher,

able heating liquid through heat exchange means 22. Additionally, the temperature within breaker 21 is such that the residual dewaxing agent admixture of urea, thiourea and acetamide is melted with the resulting formation of two liquid phases within complex breaker 21, a supernatant waxy oil phase which is withdrawn from breaker 21 via line 24 and a molten dewaxing agent phase which is withdrawn from breaker 21 via line 12 for recycle to contactor 11 to contact additional waxy charge oil.

From time to time it may be desirable to add fresh addiresulting dewaxed oil.

tor 11 to improve and expedite the complex forming reaction may be brought about by leaving behind'a portion of the solid complex after the dewaxing treatment of a waxy charge oil before fresh additional waxy charge oil is added to contactor 11, or, if desired, a portion of the solids recovered from ilter 18 via line 20, the solids comprising urea and/ or thiourea waxy complexes together Vwith solidiiied residual dewaxing agent, may be returned directly to contactor 11 via line 26.

t is seen that in the above embodiment of the practice of this invention no solvent for the dewaxing agent is employed and that substantially 100% utilization of the dewaxing agent isrealized along with substantially 100% recovery of the waxy charge oil as dewaxed oil and as waxy oil.

During the complex forming reaction carried out within contactor 11 anyv suitable Atemperature which permits the formation of solid complexes between the urea and/ or thiourea portions of the dewaxing agent and the corresponding waxy hydrocarbons in the charge oil may be employed. The complex forming Vreaction within contactor 11 is carried out at a temperature at which solid complexes are formed between the urea and/or thiourea and the waxy hydrocarbons present in the charge oil, preferably at a temperature below the initial freezing point of the dewaxing agent employed, i.e. the initial freezing point of the admixture of urea, thiourea and acetamide. Suitably, the contactor 11 during the dewaxing or cornplex forming reaction is operated at a temperature below about 120 F.

On the other hand, the complex breaker 21 or the breaking of the solid complex into the corresponding urea and/or thiourea and the waxy hydrocarbons is operated or carried out at a temperature at least above the temperature at which the formed complexes arel stable, i.e. at a temperature such that the resulting formed solid complexes decompose into their respective components. Desirably the complex breaking operation is also carried out at a temperature above the melting point of the residual dewaxing admixture of urea, thioureaY and acetamide.

A temperature substantially above the complex forming temperature employed within contactor 11, such as a temperature in the range of about 'to 100 degrees AFahrenheit above that temperature at which solids, particularly solid complexes, first appear within contactor 11. A temperature of about 125 to 150 F. is suitably employed within complex breaker 21.V

Various proportions of waxy chargeroil to dewaxing agent admixture of urea, thiourea and acetamide maybe employed in the practice of this invention provided suficient dewaxing agent is employed and is available to substantially completely remove by Vcomplex formation the waxy hydrocarbons present in the charge oil.

The practice of this invention is illustrated herewith in connection with the dewaxing of a light lubricating oil fraction. Portions of a waxy light lubricating charge oil having a pour point of 40 F. were contacted with a suitable amount of molten dewaxing agent having an initial freezing point of about 120 F., consisting of an admixture of urea, 31% thiourea and 34% acetamide, by weight, respectively. The portions of the waxy charge oil and the dewaxing agent were contacted with stirring atan initial temperature of about 120 F. andk cooled to a temperature of about 70 F.

Following the contacting operations the resulting formed solid comprising solid complexes and residual solid dewaxing agent was separately recovered from the v The resulting dewaxed oils had a pour point in the range -50 to -75 F., thereby evidencing substantially complete removal of the Wax hydrocarbonsV therefrom'.

Although emphasis has been placed in this disclosure on the applicability of this invention to the dewaxing of petroleum fractions, it is pointed out that this invention is generally applicable to the fractionation of mixtures containing components or compounds which are capable of forming solid complexes with urea and/or thiourea. Accordingly mixtures which may also be fractionated include mixtures of fatty oils or acids, tall oil, vegetable oils, fish oils, animal oils, etc.

This application is a continuation-in-part of our copending patent application Serial No. 842,313, filed September 25, V1959, nowrabandoned.

We claim; y

l. A dewaxing composition consisting essentially of an admixture of 20 to 45% by weight urea, 10 to 40% by weight thiourea and 25 to 60% by weight acetamide having a minimum melting point in the range 76 to 120 F.

2. A dewaxing composition consisting essentially of urea, thiourea and acetamide and having a minimum melting point of about 76 F., the above components being present therein in the amounts 29%, 26% and 45% by weight, respectively.

3.- A dewaxing composition having an initial freezing 20 to 45% by weight urea, l0 to 40% by weight thiourea n and 25 to 60% by weight acetamide having a minimum melting point in the range 76 to 120 F. at a temperature edective for urea to form a solid urea-waxy hydrocarbon complex with the waxy hydrocarbons in said liquid mixture, cooling the resulting reaction mixture to solidify the residual admixture of urea, thiourea and acetamide therein, filtering the resulting cooled reaction mixture to separate the solid urea-waxy hydrocarbon complex and the resulting solidified residual admixture of urea, thiourea and acet` amide and recovering a resulting treated liquid mixture having a' reduced wavy hydrocarbon content.

5. A method in accordance with claim 4 wherein the l solid urea-waxy hydrocarbon complex and the solidified resldual admixture of urea, thiourea and acetamide separated by tiltration are heated to a temperature suicient `to decompose said urea-waxy hydrocarbon complex and to liquefy the solidified residual admixture of urea, thiourea and acetamide so as to yield a two phase liquid system, a `supernatant liquid waxy phase and a liquid admixture of urea, thiourea and acetamide and separately recovering the aforesaid liquid waxy phase.

6. A method in accordance with claim 5 wherein said liquid admixture of urea, thiourea and acetamide is returned to complex additional liquid waxy mixture.

7.k A method in accordance with claim 4 wherein said admixture of urea, thiourea and acetamide has an initial freezing point below about F.

8. A method in accordance with claim 4`wherein said admixture of urea, thiourea and acetamide contains 35% by weight urea, 31% by weight thiourea and 34% by weight acetamide.

9. A method in accordance with claim 4 wherein said liquid mixture is contacted with said molten admixture of urea, thiour'ea and acetamide in the presence of solid ureawaxy hydrocarbon complex. v

10. A method of dewaxing a liquid waxy petroleum fraction which comprises contacting said petroleum fraction with a molten adrnixture consisting essentially of 20'to 45% by Weight urea, 10 to 40% by weight thiol Y urea and 25 to 60% by weight acetamide having a com'- position such that the initial freezing point of said admixture is below about 120 F., the aforesaid contacting operation being carried out in the presence of solid urea` vwaxy hydrocarbon complex, cooling the resulting reaction mixture to a temperature below the melting point of said admixture of urea, thiourea and acetamide to form `r solid urea-waxyhydrocarbon complexes between the waxy hydrocarbons in said petroleum' fraction and the urea in said' admixture and to solidify the residual admixture'of -urea, thiourea and acetamide, separating the solid urea- Y waxy hydrocarbon complex and the resulting solidified residual admixture of urea, thiourea and acetamide from the resulting treated liquid petroleum fraction and re- 2o covering said treated petroleum fraction now havingareduced waxy hydrocarbon content.

' 11. A method of dewaxing a liquid mixture containing vwaxy hydrocarbons which comprises contacting said mixture with a molten admixture consisting essentially of 2O to 45% by weight urea, l0 to 40% by Weight thiourea and 25 to `60% by weight acetamide at a tempera-v 6 ture effective to form a solidurea-.waxy hydrocarbon complex with the waxy hydrocarbons in saidliquid mixture, said admixture of urea, thiourea and acetamide being capable of forming ya three component eutectic having a melting point below about 120 F., cooling the resulting reaction mixture to solidify the residual admixture of urea,

thiourea and acetamide, ltering the resulting cooled reaction mixture to separate the solid urea-waxy hydrocarbon complex wdk the resulting solidified residual ad- References Cited in the le of this patent UNITED STATES PATENTS 2,499,820 Y Fetterly Mar.l 7, 1950 2,520,715 Fetterly Aug. 29, 1950 Tabler Nov. 17,v 1959 i OTHER REFERENCES Rogers etal.: PetroleumlRener, vol.' 36, No; 5, May

1957, pages 217 to 220. 

1. A DEWAXING COMPOSITION CONSISTING ESSENTIALLY OF AN ADMIXTURE OF 20 TO 45% BY WEIGHT UREA, 10 TO 40% BY WEIGHT THIOUREA AND 25 TO 60% BY WEIGHT ACETAMIDE HAVING A MINIMUM MELTING POINT IN THE RANGE 76 TO 120*F. 